Reproduction device and generation device

ABSTRACT

There is provided a transmitter by which a reception side easily detects packet loss of a transport packet. The transmitter ( 1 ) includes a content dividing unit ( 13 ) that divides a set composed of a plurality of units into a plurality of subsets, a transport sequence assigning unit ( 15 ) that assigns, to the packet, the transport sequence of the unit within a component and the transport sequence of the unit within the subset, and a header generating unit ( 14 ) that generates a packet including the transport sequences.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of co-pending application Ser. No.14/375,352, filed on Jul. 29, 2014, which was filed as PCT InternationalApplication No. PCT/JP2013/051708 on Jan. 28, 2013, which claims thebenefit under 350 U.S.C. § 119(a) to Patent Application No. 2012-019155,filed in Japan on Jan. 31, 2012, all of which are hereby expresslyincorporated by reference into the present application.

TECHNICAL FIELD

The present invention relates to a data structure and the like fordelivering content composed of one or more components.

BACKGROUND ART

In recent years, various types of content, such as video, sound, andtext, are being delivered. Standardization of the transport format fordelivering such content is also advancing. In particular,standardization of MPEG media transport (MPEG MMT) protocol is gainingattention.

In MPEG MMT, standardization is advancing for a transport format and thelike that efficiently deliver a plurality of components, such as video,sound, and text, over differing paths (hybrid delivery).

The content in MPEG MMT is stored as a package (MMT package) andincludes, in addition to a plurality of components (MMT assets), atleast data related to composition information (CI) and transportcharacteristics information (TC). The composition information indicatesreproduction conditions, such as layout including display position,size, and the like of each component, and whether or not components canbe combined. The transport characteristics information includes requiredbandwidth, allowable delay, and the like of each component, used todetermine the optimal delivery path.

The components included in such content can be divided into packets andtransported over a single network, or transported over a plurality ofnetworks (hybrid). This will be described with reference to FIG. 14.FIG. 14 is a diagram of content transport formats. FIG. 14(a) shows anexample of transport over a single network. FIG. 14(b) shows an exampleof hybrid transport over a plurality of networks. In FIG. 14, a singletransport packet is indicated by a single block.

In the example in FIG. 14(a), a transport packet CI for configurationinformation and a transport packet TC for transport characteristicsinformation are followed by a plurality of transport packets (A_(1,1),A_(2,1), . . . ). Transport packet A_(1,1) and subsequent transportpackets A_(i,j): i=1, 2, . . . , j=1, 2, . . . ) each include a mediaunit composing an asset. These media units are transmitted to a receiverover a network determined based on the TC, and the receiver reproducesthese media units based on the CI.

In the example in FIG. 14(a), all transport packets are delivered from atransmitter to a receiver by a single path over a single network.

On the other hand, in the example in FIG. 14(b), transport packets(A_(2,1), A_(2,3), . . . ) and (A_(2,2), A_(2,4), . . . ), obtained bydividing into two a transport packet A_(2,j) including a media unitcomposing a second asset, and transport packets (A_(1,1), A_(1,2), . . .) including media units composing a first asset are each transported ondiffering paths over differing networks. The hybrid transport is alsodescribed in PTL 1, below.

CITATION LIST Patent Literature

PTL 1: Japanese Unexamined Patent Application Publication No. 10-173612(published Jun. 26, 1998)

SUMMARY OF THE INVENTION Technical Problem

Sequence information (sequence number) is attached to each of theplurality of transport packets such as those described above. At thistime, the receiver is required to identify, on the reception side, thesequence relationship among the packets composing a component toreconstruct the component, detect packet loss, and the like. However,when a single component (asset) is divided into a plurality of subsets(sub-assets) and the sub-assets are transmitted over differing networks,a problem occurs in that the reception side cannot determine the packetsequence among the sub-assets. In addition, a problem also occurs inthat the reception side cannot determine whether or not a packet ismissing within the sub-asset.

This will be described with reference to FIG. 15. FIG. 15 is a diagramof examples of a transport packet of a conventional technology. FIG.15(a) shows an example of the transport packet when each transportpacket is given a sequence number in sub-asset units. FIG. 15(b) showsan example of the transport packet when each transport packet is given asequence number throughout the overall asset.

As shown in FIG. 15(a), the asset is composed of a sub-asset 1 and asub-asset 2. In addition, the sub-asset 1 and the sub-asset 2 aretransported over differing networks.

Furthermore, the transport packets of the sub-asset 1 and the sub-asset2 each have a transport packet format in which a header is attached to apayload. A sequence number (16 bits) is attached to each header for eachsub-asset. As shown in FIG. 15(a), sequence numbers 0x0000, 0x0001,0x0002, . . . are respectively attached to the transport packets of thesub-asset 1 in the order of transport. Similarly, sequence numbers0x0000, 0x0001, 0x0002, . . . are respectively attached to the transportpackets of the sub-asset 2 in the order of transport.

When such asset is transported, the receiver receives transport packetsthat are given the same sequence numbers. Specifically, for example, thereceiver receives the sub-asset 1 and the sub-asset 2 that each includea transport packet that is given the sequence number 0x0001. At thistime, the receiver knows that the transport packet of the sub-asset 1that is given the sequence number 0x0001 is the second packet of thesub-asset 1, and knows that the transport packet of the sub-asset 2 thatis given the sequence number 0x0001 is the second packet of thesub-asset 2. However, the receiver which has received such transportpackets cannot determine the packet sequence between the transportpacket of the sub-asset 1 that is given the sequence number 0x0001 andthe transport packet of the sub-asset 2 that is given the sequencenumber 0x0001. In this way, in the transport packet shown in FIG. 15(a),the receiver can determine the packet sequence of the received transportpackets for each sub-asset but cannot determine the packet sequencebetween sub-assets.

In addition, the asset in FIG. 15(b) is composed of the sub-asset 1 andthe sub-asset 2, in a manner similar to the asset in FIG. 15(a). Asequence number is attached to each header for each transport packetthroughout the overall asset. As shown in FIG. 15(b), because thesequence numbers are attached throughout the overall asset, no samesequence numbers are present. The transport packets of the sub-asset 1are respectively given the sequence numbers 0x0000, 0x0002, 0x0004, . .. in the order of transport, and the transport packets of the sub-asset2 are respectively given the sequence numbers 0x0001, 0x0003, 0x0005, .. . in the order of transport.

Such sub-asset 1 and sub-asset 2 are transported over differingnetworks. When the receiver receives only the sub-asset from onenetwork, such as only the sub-asset 1, the receiver receives thetransport packets given the sequence numbers 0x0000, 0x0002, 0x0004, . .. . At this time, the receiver cannot determine whether the transportpackets given the sequence numbers 0x0001, 0x0003, 0x0005, . . . areincluded in another sub-asset or packet loss has occurred.

The present invention has been achieved in light of the above-describedproblems. An object of the present invention is to provide a generationdevice and the like that generate a packet group enabling packet loss tobe easily detected when packet loss occurs, while notifying areproduction device on a reception side of an appropriate transportsequence for each packet.

Solution to Problem

To solve the above-described problems, a generation device of thepresent invention is a generation device that generates a packetincluding one of a plurality of units composing a component to transmitcontent composed of one or more components, the generation deviceincluding: a first transport sequence assigning means for assigning, tothe packet including the unit, first transport sequence informationindicating the transport sequence of the unit within the component foreach of the plurality of units; a second transport sequence assigningmeans for assigning, to the packet including the unit, second transportsequence information indicating the transport sequence of the unit foreach unit composing the content; and a packet generating means forgenerating, as the packet including the unit, a packet including thefirst transport sequence information assigned to the packet by the firsttransport sequence assigning means and the second transport sequenceinformation assigned to the packet by the second transport sequenceassigning means, for each of the plurality of units.

In addition, the generation device of the present invention is ageneration device that generates a packet including one of a pluralityof units generated by dividing a component to transmit content composedof one or more components, the generation device including: a dividingmeans for dividing a set composed of a plurality of units into aplurality of subsets; a first transport sequence assigning means forassigning, to the packet including the unit, first transport sequenceinformation indicating the transport sequence of the unit within thecomponent for each of the plurality of units; a second transportsequence assigning means for assigning, to the packet including theunit, second transport sequence information indicating the transportsequence of the unit within the subset for each unit composing thesubset, for each subset divided by the dividing means; and a packetgenerating means for generating, as the packet including the unit, apacket including the first transport sequence information assigned tothe packet by the first transport sequence assigning means and thesecond transport sequence information assigned to the packet by thesecond transport sequence assigning means, for each of the plurality ofunits.

In addition, to solve the above-described problems, a generation methodof the present invention is a generation method for a packet by ageneration device that generates a packet including one of a pluralityof units generated by dividing a component to transmit content composedof one or more components, the generation method including: a dividingstep of dividing a set composed of the plurality of units into aplurality of subsets; a first transport sequence assigning step ofassigning, to the packet including the unit, first transport sequenceinformation indicating the transport sequence of the unit within thecomponent, for each of the plurality of units; a second transportsequence assigning step of assigning, to the packet including the unit,second transport sequence information indicating the transport sequenceof the unit within the subset for each unit composing the subset, foreach subset divided at the dividing step; and a packet generating stepof generating, as the packet including the unit, a packet including thefirst transport sequence information assigned to the packet at the firsttransport sequence assigning step and the second transport sequenceinformation assigned to the packet at the second transport sequenceassigning step, for each of the plurality of units.

In the above-described configuration, a packet is generated thatincludes the first transport sequence information indicating thetransport sequence of the unit within the component for each of theplurality of units and the second transport sequence informationindicating the transport sequence of the unit within the subset for eachunit composing the subset.

Therefore, a reproduction device that has received the packet can knowthe transport sequence of the unit in component units and subset unitsfrom the transport sequence of the unit within the component and thetransport sequence of the unit within the subset.

Therefore, the reproduction device can easily determine which packet hasnot been transported, and an effect in which packet loss is easilydetected is achieved.

In addition, to solve the above-described problems, a reproductiondevice of the present invention is a reproduction device that receivesand reproduces content composed of one or more components as a packetincluding the component as a divided unit, the reproduction deviceincluding: a detecting means for detecting that the received packetincludes first transport sequence information indicating the transportsequence of the unit within the component and second transport sequenceinformation indicating the transport sequence of the unit within asubset composed of a plurality of units including the unit; and areproducing means for processing, when the detecting means detects thatthe packet includes the first transport sequence information and thesecond transport sequence information, the unit included in the packetbased on the transport sequence of the unit within the component and thetransport sequence of the unit within the subset.

In addition, to solve the above-described problems, a reproductionmethod of the present invention is a reproduction method by areproduction device that receives and reproduces content composed of oneor more components as a packet including the component as a dividedunit, the reproduction method including: a detecting step of detectingthat the received packet includes first transport sequence informationindicating the transport sequence of the unit within the component andsecond transport sequence information indicating the transport sequenceof the unit within a subset composed of a plurality of units includingthe unit; and a reproducing step of processing, when the detecting stepdetects that the packet includes the first transport sequenceinformation and the second transport sequence information, the unitincluded in the packet based on the transport sequence of the unitwithin the component and the transport sequence of the unit within thesubset.

In the above-described configuration, when the received packet includesthe transport sequence of the unit within the component and thetransport sequence of the unit within the subset, whether or not thereis a packet that has not been received can be easily determined. Inaddition, transport delay attributed to a retransmission request foralost packet can be reduced.

In addition, to solve the above-described problems, a data structure ofthe present invention is a data structure of a packet for transmittingcontent composed of one or more components, the data structureincluding: a unit generated by dividing the component; first transportsequence information indicating the transport sequence of the unitwithin the component; and second transport sequence informationindicating the transport sequence of the unit within a subset composedof a plurality of units including the unit.

The packet having the above-described data structure includes a unitgenerated by dividing a component, the first transport sequenceinformation indicating the transport sequence of the unit within thecomponent, and the second transport sequence information indicating thetransport sequence of the unit within a subset composed of a pluralityof units including the unit. Therefore, the reproduction device that hasreceived the packet having this data structure can identify thetransport sequence of the unit within the component and the transportsequence of the unit within the subset, based the first transportsequence information and the second transport sequence information.

Therefore, the reproduction device can know the transport sequence ofthe unit in component units and subset units. Therefore, thereproduction device can easily determine which packet has not beentransported and can easily detect packet loss.

The above-described generation device and reproduction device may beactualized by a computer. In this instance, a control program foractualizing the generation device and the reproduction device by acomputer by enabling the computer to operate as each means of thegeneration device and the reproduction device, and a computer-readablerecording medium in which the control program is recorded are alsoincluded in the scope of the present invention.

Advantageous Effects of Invention

As described above, the generation device of the present inventionincludes: the dividing means for dividing a set composed of a pluralityof units into a plurality of subsets; the first transport sequenceassigning means for assigning, to the packet including the unit, thefirst transport sequence information indicating the transport sequenceof the unit within the component for each of the plurality of units; thesecond transport sequence assigning means for assigning, to the packetincluding the unit, the second transport sequence information indicatingthe transport sequence of the unit within the subset for each unitcomposing the subset, for each subset divided by the dividing means; andthe packet generating means for generating, as the packet including theunit, a packet including the first transport sequence informationassigned to the packet by the first transport sequence assigning meansand the second transport sequence information assigned to the packet bythe second transport sequence assigning means, for each of the pluralityof units.

In addition, the generation method of the present invention includes:the dividing step of dividing a set composed of the plurality of unitsinto a plurality of subsets; the first transport sequence assigning stepof assigning, to the packet including the unit, the first transportsequence information indicating the transport sequence of the unitwithin the component, for each of the plurality of units; the secondtransport sequence assigning step of assigning, to the packet includingthe unit, the second transport sequence information indicating thetransport sequence of the unit within the subset for each unit composingthe subset, for each subset divided at the dividing step; the packetgenerating step of generating, as the packet including the unit, apacket including the first transport sequence information assigned tothe packet at the first transport sequence assigning step and the secondtransport sequence information assigned to the packet at the secondtransport sequence assigning step, for each of the plurality of units.

In addition, the reproduction device of the present invention includes:the detecting means for detecting that the received packet includes thefirst transport sequence information indicating the transport sequenceof the unit within the component and the second transport sequenceinformation indicating the transport sequence of the unit within asubset composed of a plurality of units including the unit; and thereproducing means for processing, when the detecting means detects thatthe packet includes the first transport sequence information and thesecond transport sequence information, the unit included in the packetbased on the transport sequence of the unit within the component and thetransport sequence of the unit within the subset.

In addition, the reproduction method of the present invention includes:the detecting step of detecting that the received packet includes thefirst transport sequence information indicating the transport sequenceof the unit within the component and the second transport sequenceinformation indicating the transport sequence of the unit within asubset composed of a plurality of units including the unit; and thereproducing step of processing, when the detecting step detects that thepacket includes the first transport sequence information and the secondtransport sequence information, the unit included in the packet based onthe transport sequence of the unit within the component and thetransport sequence of the unit within the subset.

In addition, the data structure of the present invention includes: aunit generated by dividing the component; the first transport sequenceinformation indicating the transport sequence of the unit within thecomponent; and the second transport sequence information indicating thetransport sequence of the unit within a subset composed of a pluralityof units including the unit.

Therefore, the reproduction device can easily deteiinine which packethas not been transported, and an effect in which packet loss can beeasily detected is achieved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a configuration of main sections of atransmitter and a receiver configuring a content transmitting systemaccording to an embodiment of the present invention.

FIG. 2 is a diagram of an example of a data structure of contentsupported by the content transmitting system.

FIG. 3 is a diagram of an example of a transport format of the content.

FIG. 4 is a diagram of an example of a transport packet including packetsequence information.

FIG. 5 is a diagram of an example of a structure (syntax) of a transportpacket header of the transport packet in FIG. 4.

FIG. 6 is a diagram of another example of a transport packet includingthe packet sequence information.

FIG. 7 is a diagram of an example of a structure (syntax) of a transportpacket header of the transport packet in FIG. 6.

FIG. 8 is a diagram of an example of composition information.

FIG. 9 is a flowchart of an example of a transport packet generationprocess performed by the transmitter.

FIG. 10 is a flowchart of an example of a reproduction process performedby the receiver.

FIG. 11 is a diagram of an example of a transport packet when the sametransport packet is included in a plurality of sub-assets.

FIG. 12 is a diagram of an example of a transport packet when coded datais included as a transport packet in a plurality of sub-assets.

FIG. 13 is a diagram of an example of a transport packet when aplurality of assets are divided into a plurality of sub-assets.

FIG. 14 is a diagram of conventionally used content transport formats,in which FIG. 14(a) shows an example of transport over a single networkand FIG. 14(b) shows an example of hybrid transport over a plurality ofnetworks.

FIG. 15 is a diagram of examples of a transport packet of a conventionaltechnology, in which FIG. 15(a) shows an example of the transport packetwhen each transport packet is given a sequence number in sub-asset unitsand FIG. 15(b) shows an example of the transport packet when eachtransport packet is given a sequence number throughout the overallasset.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will hereinafter be described indetail with reference to FIG. 1 to FIG. 13.

[System Configuration]

First, a configuration of a content transmitting and receiving systemaccording to the present embodiment will be described with reference toFIG. 1. FIG. 1 is a block diagram of a configuration of main sections ofa transmitter (generation device) 1 and a receiver (reproduction device)2 configuring a content transmitting and receiving system 3.

As shown in FIG. 1, the content transmitting and receiving system 3 isconfigured by the transmitter 1 and the receiver 2 being connected by anetwork. In the content transmitting and receiving system 3, thereceiver 2 receives and reproduces content transmitted by thetransmitter 1.

In the example in FIG. 1, the transmitter 1 and the receiver 1communicate directly. However, communication is not limited thereto. Forexample, a relay device may relay communication between the transmitter1 and the receiver 2. Alternatively, the transmitter 1 may delivercontent to another delivery server, and the content may be delivered tothe receiver 2 from the delivery server.

In addition, here, an example in which the network connecting thetransmitter 1 and the receiver 2 is the Internet is described. However,the network is merely required to enable the transmitter 1 and thereceiver 2 to transmit and receive content, and is not limited to theInternet. For example, a broadcast network may be used as the network.Alternatively, hybrid delivery in which the Internet and a broadcastnetwork are used in combination may be performed.

The transmitter 1 is a device that delivers content. The transmitter 1includes a transmitter control unit 10 that supervises and controls thefunctions of the transmitter 1, a transmitter storage unit 11 thatstores therein data transmitted by the transmitter 1, and a transmittercommunication unit 12 that enables the transmitter 1 to communicate withan external device.

In addition, the transmitter control unit 10 includes a content dividingunit (dividing means) 13, a header generating unit (packet generatingmeans) 14, and a transport sequence assigning unit (first transportsequence assigning means and second transport sequence assigning means)15. Content 16 is stored in the transmitter storage unit 11.

The content dividing unit 13 divides the content 16 for delivery.Specifically, for example, the content dividing unit 13 divides acomponent of the content into media unit units, thereby generating mediaunits. In addition, the content dividing unit 13 divides the componentinto a plurality of subsets. Specifically, the content dividing unit 13divides a set (asset) composed of a plurality of media units into aplurality of subsets (sub-assets). In addition, the content dividingunit 13 identifies and extracts composition information (CI;reproduction information), transport characteristics information (TC),and the like from the content 16. Details of the media unit, thecomposition information, and the transport characteristics informationwill be described hereafter.

The transport sequence assigning unit 15 assigns, to a packet includinga media unit, information (first transport sequence information)indicating the transport sequence of the media unit within thecomponent, for each of the plurality of media units generated by thecontent dividing unit 13.

In addition, the transport sequence assigning unit 15 assigns, to apacket including a media unit, information (second transport sequenceinformation) indicating the transport sequence of the media unit withinthe sub-asset, for each media unit composing the sub-asset, for eachsub-asset.

The transport sequence assigning unit 15 supplies the header generatingunit with the first transport sequence information and the secondtransport sequence information assigned to each packet.

The header generating unit 14 generates a header to be attached to thedata generated by the content dividing unit 13. Specifically, the headergenerating unit 14 generates a payload format header including at leastinformation indicating the payload type. The header generating unit 14adds the payload format header to the media unit, the compositioninformation, and the transport characteristics information,respectively, and generates a payload.

In addition, the header generating unit 14 generates a transport packetheader for each packet to be delivered. The header generating unit 14adds the transport packet header to the payload and generates atransport packet. The transport packet header includes the firsttransport sequence information and the second transport sequenceinformation supplied from the transport sequence assigning unit 15. Thefirst transport sequence information and the second transport sequenceinformation are hereinafter referred to as packet sequence information.

The content 16 is the content to be delivered by the transmitter 1. Asdescribed above, the content 16 is divided by the content dividing unit13, a header is attached thereto by the header generating unit 14, andis delivered as a transport packet.

On the other hand, the receiver 2 is a device that receives andreproduces content. The receiver 2 includes a receiver control unit 20that supervises and controls the functions of the receiver 2, a receiverstorage unit 21 that stores therein data received by the receiver 2, areceiver communication unit 22 that enables the receiver 2 tocommunicate with an external device, a display unit 23 that displays animage, and a sound output unit 24 that outputs sound.

In addition, the receiver control unit 20 includes a header analyzingunit (detecting means) 25, a decoder 26, and a reproduction control unit(reproducing means) 27.

The header analyzing unit 25 analyzes the header of a received transportpacket and performs a process based on the analysis result.Specifically, when packet loss is detected, such as a discontinuity inthe packet sequence information (intra sequence number and/or intersequence number, described hereafter), the header analyzing unit 25instructs the receiver communication unit 22 to make a retransmissionrequest. In addition, when the analyzed header indicates that a mediaunit is included as the payload, the header analyzing unit 25 transmitsthe payload to the decoder 26 for decoding. On the other hand, when theanalyzed header indicates that composition information is included asthe payload, the header analyzing unit 25 transmits the payload to thereproduction control unit 27.

The decoder 26 decodes the media unit included in the received transportpacket. The decoded data is outputted from the display unit 23 and thesound output unit 24 under the control of the reproduction control unit27.

The reproduction control unit 27 reproduces the component based on thecomposition information. Specifically, the reproduction control unit 27outputs the media unit decoded by the decoder 26 from the display unit23 and the sound output unit 24, based on the composition information.

[Content Data Structure]

Next, the data structure of the content 16 will be described withreference to FIG. 2. FIG. 2 is a diagram of an example of the datastructure of the content 16.

The content 16 is stored in the transmitter storage unit 11 as a packageincluding a header, the composition information (CI), the transportcharacteristics information (TC), and a plurality of assets.

The asset is a component, such as video, sound, or text, and is composedof a header and a plurality of media units (M-unit: MU). In addition,the media unit is a unit serving as the unit for random access andtime-stamp attachment, and is composed of a header and a plurality ofmedia fragment units (MFU).

The composition information indicates the reproduction format of thecomponent. Specifically, the composition information indicates layout,such as the display position and display size of each component, whetheror not components can be combined (whether or not a component can besimultaneously reproduced with another component), and the like. Eachmedia unit is reproduced with reference to the composition information.

The transport characteristics information indicates the transportcharacteristics of each component. Specifically, the transportcharacteristics information indicates required bandwidth, allowabledelay, and the like of each component, used to determine the optimaldelivery path.

[Content Transport Format]

Next, a transport format of the content 16 will be described withreference to FIG. 3. FIG. 3 is a diagram of an example of the transportformat of the content 16.

When the content 16 is transported by TCP/IP, UDP/IP, or the like, theformat is a transport packet in which a header is attached to thepayload. The above-described packet sequence information is written inthe header of the payload.

In addition, the payload format when the package of the content 16 isdelivered is that in which a header is attached to the media unit (MU),the composition information (CI), and the transport characteristicsinformation (TC), respectively, as shown in FIG. 3.

In the payload format in FIG. 3, a single media unit serves as a singlepayload. However, this is not limited thereto. For example, when thesize of the transport packet is restricted, the media unit may befurther divided, and the divided media units may each be transported asdiffering payloads. Alternatively, a plurality of media units may becollectively transported as a single payload. In this instance, aconfiguration may be used in which a flag indicating whether or not thefirst media fragment unit composing the media unit is included, a flagindicating whether or not the last media fragment unit composing themedia unit is included, and the like are written in the payload formatheader.

[Details of Packet Sequence Information]

Next, details of the packet sequence information will be described withreference to FIG. 4 to FIG. 7.

(Specific Example 1 of Packet Sequence Information)

FIG. 4 is a diagram of an example of a transport packet including thepacket sequence information. FIG. 4 shows transport packets that areincluded in an asset composed of a sub-asset 1 and a sub-asset 2. Ineach transport packet, a 16-bit header is attached to the payload. Asthe packet sequence information, the header includes an 8-bit intrasequence number (second transport sequence information) indicating thetransport sequence of the transport packet within the sub-asset for eachsub-asset, and an 8-bit inter sequence number (first transport sequenceinformation) indicating the transport sequence of the transport packetwithin the asset.

As shown in FIG. 4, the sub-asset 1 includes transport packets of whichthe intra sequence numbers are 0x00, 0x01, 0x02, . . . . In addition,the sub-asset 2 includes transport packets of which the intra sequencenumbers are 0x00, 0x01, 0x02, . . . . The receiver 2 can detect amissing number within the sub-asset (missing packet) by analyzing theintra sequence number.

In addition, the sub-asset 1 includes transport packets of which theinter sequence numbers are even numbers (0x00, 0x02, 0x04, . . . ). Thesub-asset 2 includes transport packets of which the inter sequencenumbers are odd numbers (0x01, 0x03, 0x05, . . . ). The receiver 2 candetermine the sequence in which to transport the transport packets ofthe asset by analyzing such inter sequence numbers.

FIG. 5 is a diagram of an example of a structure (syntax) of a transportpacket header of the transport packet in FIG. 4.

In the transport packet header structure in FIG. 5, if inter_flag==‘1’follows a 1-bit flag inter_flag, an 8-bit value intra_sequence_numberindicating the intra sequence number and an 8-bit value intersequence_number indicating the inter sequence number follow. Inaddition, if inter_flag==‘1’ does not follow the 1-bit flag inter_flag,a 16-bit value sequence_number indicating a sequence number similar to aconventional sequence number follows.

In this way, the header generating unit 14 can generate a transportpacket including the intra sequence number and the inter sequence numberindividually.

As a result, the receiver 2 that has received the transport packet canrecognize the transport sequence of the transport packet within theasset and the transport sequence of the transport packet within thesub-asset.

(Specific Example 2 of Packet Sequence Information)

FIG. 6 is a diagram of another example of the transport packet includingthe packet sequence information. FIG. 6 shows transport packets that areincluded in an asset composed of the sub-asset 1 and the sub-asset 2. Ineach transport packet, a 16-bit header is attached to the payload. Asthe packet sequence information, a 16-bit concatenated sequence numberis written in the header. The eight low-order bits of the concatenatedsequence number include the intra sequence number indicating thetransport sequence of the transport packet within the sub-asset, foreach sub-asset. In addition, the eight high-order bits of theconcatenated sequence number include the inter sequence numberindicating the transport order of the transport packet within the asset.

As shown in FIG. 6, the sub-asset 1 includes transport packets of whichthe eight low-order bits (intra sequence number) of the concatenatedsequence number are 00, 01, 02, . . . . In addition, the sub-asset 2includes transport packets of which the eight low-order bits (intrasequence number) of the concatenated sequence number are 00, 01, 02, . .. . The receiver 2 can detect a missing number within the sub-asset(missing packet) by analyzing the eight low-order bits (intra sequencenumber) of the concatenated sequence number.

In addition, the sub-asset 1 includes transport packets of which theeight high-order bits (inter sequence number) of the concatenatedsequence number are even numbers (0x00, 0x02, 0x04, . . . ). Thesub-asset 2 includes transport packets of which the eight high-orderbits (inter sequence number) of the concatenated sequence number are oddnumbers (0x01, 0x03, 0x05, . . . ). The receiver 2 can determine thesequence in which to transport the transport packets of the asset byanalyzing such inter sequence numbers.

FIG. 7 is a diagram of an example of a structure (syntax) of a transportpacket header of the transport packet in FIG. 6.

In the transport packet header structure in FIG. 7, if aconcatenated_flag==‘1’ follows a 1-bit flag concatenated_flag, a 16-bitvalue concatenated_sequence_number indicating the concatenated sequencenumber follows. In addition, if the concatenated_flag==‘1’ does notfollow the 1-bit flag concatenated_flag, a 16-bit value sequence_numberindicating a sequence number similar to a conventional sequence numberfollows.

In this way, the header generating unit 14 can generate a transportpacket including a concatenated sequence number that incorporates theintra sequence number and the inter sequence number.

As a result, the receiver 2 that has received the transport packet canrecognize the transport sequence of the transport packet within theasset and the transport sequence of the transport packet within thesub-asset.

In the description above, the transport packets of which the intersequence number is an even number are included in the sub-asset 1 andthe transport packets of which the inter sequence number is an oddnumber are included in the sub-asset 2. However, the sub-asset in whicha transport packet is included is not limited thereto and is arbitrary.

[Specific Example of Composition Information]

Next, a specific example of the composition information will bedescribed with reference to FIG. 8. FIG. 8 is a diagram of an example ofthe composition information.

In the composition information shown in FIG. 8, a region r1(corresponding to full screen display) and a region r2 (corresponding toan upper left region when the display screen is divided vertically andlaterally into four regions) are defined by a <layout> tag. A sub-asseta11 and a sub-asset a12 are associated with the region r1 by a <union>tag designating uniting of the sub-assets composing an asset. Inaddition, whether a sub-asset a21 can be displayed in the region r2 or asub-asset a22 can be displayed in the region r2 is defined by an <excl>tag designating mutually exclusive display of the asset. In addition, adescription (start=“0 s”) that indicates that the layout is applied fromtime 0 s is included.

Therefore, simultaneously with the start of reproduction of the contentincluding the sub-assets a11, a12, a21, and a22, the receiver 2 unitesthe sub-assets a11 and a12 and performs full-screen display thereof, andreduces the sub-asset a21 or a22 to one-fourth and displays thesub-asset a21 or a22 in the upper left of the screen, as shown in FIG.8.

In FIG. 8, an example in which the composition information is written insynchronized multimedia integration language (SMIL) is shown. However,the composition information is merely required to indicate the displayformat of the asset, and the writing format thereof is not particularlylimited.

[Flow of Transport Packet Generation Process]

Next, the flow of a transport packet generation process (packetgeneration method) performed by the transmitter 1 will be described withreference to FIG. 9. FIG. 9 is a flowchart of an example of thetransport packet generation process. The timing at which the transportpacket generation process is performed is not particularly limited. Forexample, in on-demand delivery, the transport packet generation processmay be performed when a transmission request for content is receivedfrom the receiver 2. In live delivery, the transport packet generationprocess may be performed when the content is coded.

First, the content dividing unit 13 reads out the content 16 stored inthe transmitter storage unit 11 and generates a payload (strictlyspeaking, data stored in the payload portion of the transport packet inFIG. 3). Specifically, the content dividing unit 13 acquires the assetfrom the content 16 stored as a package, as shown in FIG. 2, andgenerates a plurality of payloads by dividing the acquired asset (S91).Then, the content dividing unit 13 outputs the plurality of payloadsgenerated as described above to the header generating unit 14.

The unit by which the asset is divided into payloads is not limited tothe media unit. For example, when the size of the payload is restricted,the payload may be the media unit further divided into a predeterminedsize. In addition, when minimization of the overhead for division or thelike is desired, a plurality of media units may be combined to form asingle payload. Furthermore, the content dividing unit 13 extracts thecomposition information (CI) and the transport characteristicsinformation (TC) included in the package from the content 16 and outputsthe composition information (CI) and the transport characteristicsinformation (TC) to the header generating unit 14.

Next, the header generating unit 14 generates the payload format thatincludes information indicating the payload type from the plurality ofpayloads that have been inputted (S92). Specifically, the headergenerating unit 14 generates the payload format header in whichinformation (payload_type=MU) indicating that the payload type is mediaunit is written. The header generating unit 14 attaches the payloadformat header to each media unit and generates the payload format suchas that shown in FIG. 3.

The payload type of the payload format is based on the data receivedfrom the content dividing unit 13. For example, when the compositioninformation is inputted from the content dividing unit 13, a payloadformat header is generated in which the information (payload_type=CI)indicating that the payload type is composition information is written.Similarly, when the transport characteristics information (TC) isinputted, a payload format header is generated in which the information(payload_type=TC) indicating that the payload type is transportcharacteristics information is written.

Next, the content dividing unit 13 divides the acquired asset intosub-assets (subsets). Specifically, the content dividing unit 13 divideseach of the plurality of payloads generated at S91 into a plurality ofsub-assets (S93; dividing step).

Next, the transport sequence assigning unit 15 assigns information(inter sequence number) indicating the transport sequence of the payloadwithin the content (asset), to each of the plurality of payloads dividedby the content dividing unit 13 (S94; first transport sequence assigningstep). In addition, the transport sequence assigning unit 15 assignsinformation (intra sequence number) indicating the transport sequence ofthe payload within the sub-asset to each of the plurality of payloadsdivided by the content dividing unit 13 (S95; second transport sequenceassigning step).

Then, the header generating unit 14 generates a transport packet headerincluding the inter sequence number and the intra sequence numberassigned to each payload at S94 and S95, adds the transport packetheader to the payload format generated at S92, and generates a transportpacket such as that shown in FIG. 3 (S96; packet generating step).

Then, the header generating unit 14 outputs the generated transportpacket to the transmitter communication unit 12 (S97), and the transportpacket generation process is completed. As a result, the transportpacket generated as described above is transmitted over the network tothe receiver 2.

In this way, the transmitter 1 of the present invention generates atransport packet including the inter sequence number indicating thetransport sequence of the payload within the asset and the intrasequence number indicating the transport sequence of the payload withinthe sub-asset, for each of the plurality of payloads.

Therefore, the receiver 2 that has received the transport packet canknow the transport sequence of the payload in asset units and sub-assetunits based on the transport sequence of the payload within the assetand the transport sequence of the payload within the sub-asset. As aresult, the receiver 2 can easily determine which transport packet hasnot been transported and an effect in which packet loss can be easilydetected is achieved.

[Flow of Reproduction Process]

Next, the flow of a reproduction process (reproduction method) performedby the receiver 2 will be described with reference to FIG. 10. FIG. 10is a flowchart of an example of the reproduction process. In FIG. 10, aprocess from the reception of a single transport packet to outputthereof is described. The transport packet header structure shown inFIG. 5 is used.

The receiver communication unit 22 receives the transport packettransmitted from the transmitter communication unit 12 of thetransmitter 1 over the network (S100) and outputs the transport packetto the header analyzing unit 25. Then, the header analyzing unit 25analyzes the header (transport packet header) of the received transportpacket (S101) and determines whether the inter_flag==‘1’ (S102;detecting step).

As a result of the analysis, when confirmed that the inter_flag==‘1’(Yes at S102), the header analyzing unit 25 acquires the inter sequencenumber and the intra sequence number included in the transport packetheader (S103). On the other hand, when the inter_flag is notinter_flag==‘1’ (No at S102), the header analyzing unit 25 acquires thesequence number included in the transport packet header (S104).

Next, the header analyzing unit 25 detects whether or not packet losshas occurred based on the sequence number acquired at S103 or S104 andthe sequence number of a previously received transport packet (S105;detecting step). When a packet loss is detected (Yes at S105), theheader analyzing unit 25 instructs the receiver communication unit 22 tomake a retransmission request for the lost packet (S106). In particular,if the loss of a plurality of packets is detected when theinter_flag==‘1’, the retransmission request is made starting from thepacket with the smaller inter sequence number. As a result, transportdelay attributed to retransmission can be reduced.

After S105 or S106 is completed, the header analyzing unit 25 analyzesthe payload format header (S107) and determines whether or not thepayload_type==MU (S108). When the payload_type==MU (Yes at S108), theheader analyzing unit 25 outputs, to the decoder 26, the media unitincluded in the transport packet to which the payload format header isattached (S109).

As a result, the media unit is decoded and outputted from the displayunit 23 and/or the sound output unit 24 based on the compositioninformation, under the control of the reproduction control unit 27(reproduction step). The reproduction process is thereby completed.

On the other hand, as a result of the analysis at S107, when thepayload_type is not payload_type==MU (No at S108), the header analyzingunit 25 outputs the payload to each processing unit based on thepayload_type (S110). For example, when the payload_type==CI, because thepayload includes the composition information, the payload is transmittedto the reproduction control unit 27 and the reproduction control unit 27makes settings. The reproduction process is thereby completed.

In this way, when the received transport packet includes the transportsequence of the payload within the asset and the transport sequence ofthe payload within the sub-asset, the receiver 2 of the presentinvention can easily determine whether or not there is a transportpacket that has not been received and can reduce the transport delayattributed to the retransmission request for the lost packet.

[Variation Example: Allocated Bits for Inter Sequence Number and IntraSequence Number]

In the description above, the inter sequence number and the intrasequence number are both allocated eight bits. However, bit allocationsof the inter sequence number and the intra sequence number are notlimited thereto. The bit allocations of the inter sequence number andthe intra sequence number may be equal. Alternatively, either of theinter sequence number and the intra sequence number may be allocated alarger number of bits.

For example, when the number of divisions into sub-assets increases, theinter sequence number may be allocated more bits than the intra sequencenumber. For example, the inter sequence number may be allocated ten bitsand the intra sequence number may be allocated six bits.

Alternatively, the number of bits may be dynamically changed byinformation indicating an allocation pattern for the inter sequencenumber and the intra sequence number being added to the transport packetheader or the like. In this instance, the receiver 2 side analyzes thetransport packet header to which the information indicating theallocation pattern is attached, thereby confirming the number of bitsrespectively allocated to the inter sequence number and the intrasequence number.

[Variation Example: Division of Transport Packet Into Sub-Assets]

In the description above, an asset is divided into two sub-assets.However, the number of sub-assets into which an asset can be divided isnot limited to two, and is arbitrary. In addition, it is described thata transport packet is included in any one sub-asset. However, atransport packet may be included in a plurality of sub-assets. This willbe described with reference to FIG. 11.

FIG. 11 is a diagram of an example of a transport packet when the sametransport packet is included in a plurality of sub-assets. As shown inFIG. 11, the asset is composed of the sub-asset 1 and the sub-asset 2.The sub-asset 1 includes transport packets of which the intra sequencenumbers are 0x00, 0x01, 0x02, . . . , and the inter sequence numbers are0x00, 0x02, 0x04, . . . . In addition, the sub-asset 2 includestransport packets of which the intra sequence numbers are 0x00, 0x01,0x02, 0x03, . . . , and the inter sequence numbers are 0×01, 0x02, 0x03,0x05, . . . .

As shown in FIG. 11, the sub-asset 1 and the sub-asset 2 both includetransport packets that are given the same inter sequence number (0x02 inthe example in FIG. 11). The inter sequence number indicates thetransport sequence of the transport packet within the asset. Therefore,it is clear that transport packets having the same inter sequence numberare the same packet.

In this way, as a result of the transport packets being made redundantby the same transport packet being included in a plurality ofsub-assets, an effect in which tolerance to packet loss is increased isachieved.

[Variation Example: Sub-Asset Division Variation 1]

The content dividing unit 13 may divide the content into intra codeddata (intra-frame compression-coded data) and inter coded data(inter-frame compression-coded data). The content dividing unit 13 maythen include the intra coded data and inter coded data in differingsub-assets, and transport the sub-assets. This will be described withreference to FIG. 12.

FIG. 12 is a diagram of an example of a transport packet when coded datais included in a plurality of sub-assets as a transport packet. As shownin FIG. 12, the asset is composed of the sub-asset 1 and the sub-asset2. The sub-asset 1 includes transport packets of intra coded data. Inaddition, the sub-asset 2 includes transport packets of inter codeddata. The transport packets included in the sub-asset 1 and thesub-asset 2 are transport packets that include the above-described intersequence number and intra sequence number. FIG. 12 shows an example inwhich the inter sequence number and the intra sequence number areindividually added to the payload. However, a concatenated sequencenumber incorporating the inter sequence number and the intra sequencenumber may be attached to the payload as shown in FIG. 6. Thetransmitter 1 transmits such asset.

When a user views content and performs a trick play such asfast-forward, the receiver 2 is merely required to receive the sub-asset1. Even when a packet loss is detected in the transport packets of thesub-asset 2, the receiver 2 does not need to make a retransmissionrequest for the transport packet. In addition, when the user is viewingcontent by normal playback, the receiver 2 is required to receive boththe sub-asset 1 and the sub-asset 2. However, when packet loss isdetected, decrease in overall quality can be suppressed by the receiver2 preferentially making the retransmission request for the transportpacket of the sub-asset 1.

In addition, the receiver 2 can easily know which packet has not beentransported by analyzing the intra sequence numbers and the intersequence numbers.

In this way, the asset in the present variation example is an asset thathas been predictive-coded by combined use of a plurality of predictionmethods (such as intra coding and inter coding). The content dividingunit 13 can divide an asset into a plurality of sub-assets in which eachsub-asset is composed of units coded using the same prediction method.

[Variation Example: Sub-Asset Division Variation 2]

The content dividing unit 13 may perform hierarchical coding (such astime scalability) of content. The content dividing unit 13 may theninclude base-layer data (low frame rate video) and enhancement-layerdata (differential video for high frame rate video) in differingsub-assets, and transport the sub-assets.

For example, as shown in FIG. 12, the sub-asset 1 includes transportpackets of base-layer data and the sub-asset 2 includes the transportpackets of enhancement-layer data. The transport packets included in thesub-asset 1 and the sub-asset 2 are transport packets that include theabove-described inter sequence number and intra sequence number. FIG. 12shows an example in which the inter sequence number and the intrasequence number are individually added to the payload. However, aconcatenated sequence number incorporating the inter sequence number andthe intra sequence number may be attached to the payload as shown inFIG. 6. The transmitter 1 transmits such asset.

When the user views content, if the content is played back as a lowframe rate video, the receiver 2 is merely required to receive thesub-asset 1. Even when a packet loss is detected in the transportpackets of the sub-asset 2, the receiver 2 does not need to make aretransmission request for the transport packet. In addition, when theuser plays back the content as a high frame rate video, the receiver 2is required to receive both the sub-asset 1 and the sub-asset 2.However, when packet loss is detected, decrease in overall quality canbe suppressed by the receiver 2 preferentially making the retransmissionrequest for the transport packet of the sub-asset 1.

In addition, the receiver 2 can easily know which packet has not beentransported by analyzing the intra sequence numbers and the intersequence numbers.

In this way, the plurality of payloads in the present variation exampleis composed of payloads of a plurality of layers having differingqualities such as frame rate. The content dividing unit 13 can divide anasset into a plurality of sub-assets in which each sub-asset is composedof payloads of the same layer.

[Variation Example: Sub-Asset Division Variation 3]

In the description above, the transmitter 1 generates a packet includingone of a plurality of media units generated by dividing a single assetcomposing the content. However, the transmitter 1 may generate a packetincluding one of a plurality of media units generated by dividing eachof a plurality of assets composing the content. This will be describedwith reference to FIG. 13.

FIG. 13 is a diagram of an example of a transport packet when aplurality of assets are divided into a plurality of sub-assets. As shownin FIG. 13, a concatenated sequence number is attached to the payload.The eight high-order bits of the concatenated sequence number indicatesthe inter sequence number. The subsequent six bits indicate the intrasequence number, and the two low-order bits indicate an asset ID(component information). Asset 1 (Asset ID=1) is a component in whichvideo data and audio data are multiplexed. Specifically, the asset 1includes video data (V) and English audio data (A). In addition, asset 2(Asset ID=2) is a component composed of subtitle data in a plurality oflanguages, including Japanese subtitle data (T). Furthermore, thesub-asset 1 includes the video data (V) of the asset 1, and thesub-asset 2 includes the English audio data (A) of the asset 1 and theJapanese subtitle data (T) of the asset 2. The transmitter 1 transmitssuch assets.

The receiver 2 is required to receive both the sub-asset 1 and thesub-asset 2 for normal reproduction (reproduction using the video dataand the audio data). However, when the subtitle is not displayed, or inother words, when the packets of the asset 2 are not used, the receiver2 references the two low-order bits of the concatenated sequence numberand destroys the packets including the subtitle data. In the data of theasset 2 shown in FIG. 13, the eight high-order bits (inter sequencenumber) of the concatenated sequence number are 0x01, 0x03, . . . andpackets with 0x00 and 0x02 are not received. However, because the asset2 is data that is not to be used, even when a packet loss in the data ofthe asset 2 is detected, the receiver 2 does not need to requestretransmission of the transport packet from the transmitter 1.

In this way, in the present variation example, division is performedsuch that a plurality of payloads of a plurality of assets are includedin a certain sub-asset (such as the sub-asset 2). The divided payloadgenerates a transport packet including information (inter sequencenumber) indicating the transport sequence of the payload within theplurality of assets, information (intra sequence number) indicating thetransport sequence of the payload within the sub-asset 2, and the assetID indicating the asset of the payload among the plurality of assets.

Therefore, the receiver 2 that has received the transport packet ismerely required to receive only the transport packets of the requiredasset (such as the asset 1) by referencing the asset ID. The process forrequesting retransmission of a transport packet from the transmitter 1when a transport packet of another asset (such as the asset 2) is notreceived can be omitted.

[Subject Performing Transport Packet Delivery]

In the description above, the transmitter 1 both generates and deliversthe transport packet. However, the transport packet may be generated anddelivered by differing devices. Alternatively, generation and deliveryof transport packets may be each be performed by a plurality of devices.For example, a transport packet of content for broadcast delivery may begenerated by a certain device, and a transport packet of content foron-demand delivery (such as communication delivery) may be generated byanother device. In this instance, a transport packet including thepacket sequence information may be generated in either of the certaindevice and the other device.

The present invention is not limited to the above-described embodimentand various modifications are possible within the scope indicated in theclaims. In other words, embodiments achieved by combining technicalmeans modified accordingly within the scope indicated by the claims arealso included in the technical scope of the present invention.

[Example of Actualization by Software]

Finally, each block of the transmitter 1 and the receiver 2,particularly the transmitter control unit 10 and the receiver controlunit 20, may be actualized by hardware by a logic circuit formed on anintegrated circuit (IC) chip, or may be actualized by software using acentral processing unit (CPU).

In the latter instance, the transmitter 1 and the receiver 2 eachinclude a CPU that executes commands in a program that actualizes eachfunction, a read-only memory (ROM) storing therein the program, a randomaccess memory (RAM) in which the program is expanded, a storage device(recording medium), such as a memory, storing therein the program andvarious pieces of data, and the like. The object of the presentinvention can be achieved by the transmitter 1 and the receiver 2 eachbeing provided with a recording medium in which program codes(executable program, intermediate code program, and source program) ofthe control programs of the transmitter 1 and the receiver 2 that aresoftware actualizing the above-described functions is recorded, in acomputer-readable manner, and a computer (or CPU or MPU) reading andrunning the program codes recorded in the recording medium.

As the recording medium, for example, tapes, such as a magnetic tape ora cassette tape, disks including magnetic disks, such as a floppy® diskor a hard disk, and optical disks, such as CD-ROM/MO/MD/DVD/CD-R, cards,such as an IC card (including memory card)/optical card, semiconductormemories, such as mask ROM/EPROM/EEPROM/flash ROM, or logic circuits,such as a programmable logic device (PLD) or a field programmable gatearray (FPGA), can be used.

In addition, the transmitter 1 and the receiver 1 may be configured tobe connectable to a communication network, and the program codes may beprovided via the communication network. The communication network inthis instance is merely required to be capable of transmitting theprogram codes and is not particularly limited. For example, theInternet, intranets, extranets, LAN, ISDN, VAN, CATV communicationnetworks, virtual private networks, telephone line networks, mobilecommunication networks, satellite communication networks, and the likecan be used. In addition, a transmission medium configuring thecommunication network is merely required to be a medium capable oftransmitting the program codes and is not limited to a particularconfiguration or type. For example, wired media such as IEEE1394, USB,power line carriers, cable TV channels, telephone lines, and asymmetricdigital subscriber line (ADSL), and wireless media such as infraredmedia like IrDA or remote control, Bluetooth®, IEEE802.11 wireless, highdata rate (HDR), near field communication (NFC), digital living networkalliance (DLNA), mobile phone networks, satellite channels, andterrestrial digital networks can be used. The present invention can alsobe actualized in the form of computer data signals embedded in carrierwaves in which program codes are embodied by electronic transport.

[Notes Related to the Present Invention]

The packet generating means of the generation device of the presentinvention preferably individually includes the first transport sequenceinformation and the second transport sequence information in the packet.In addition, the packet generating means of the generation device of thepresent invention may collectively include the first transport sequenceinformation and the second transport sequence information in the packet.

In the above-described configuration, the generation device is capableof generating a packet in which the first transport sequence informationand the second transport sequence information are individually included,or a packet in which the first transport sequence information and thesecond transport sequence information are collectively included.

Therefore, the reproduction device that has received the packet can knowthe transport sequence of the unit in the component of the unit and thetransport sequence of the unit in the subset, regardless of whether thepacket includes the first transport sequence information and the secondtransport sequence information individually, or the packet includes thefirst transport sequence information and the second transport sequenceinformation collectively.

In addition, the component of the generation device of the presentinvention is a component that is predictive-coded by combined use of aplurality of prediction methods. The dividing means may be configured todivide a set composed of the plurality of units into a plurality ofsubsets in which each subset is composed of units that arepredictive-coded using the same prediction method.

In the above-described configuration, the generation device divides, forexample, intra-frame compression-coded data and inter-framecompression-coded data into differing subsets.

Therefore, the reproduction device can select whether to receive onlyeither of the intra-frame compression-coded data and the inter-framecompression-coded data that use differing prediction methods, or both.

In addition, the plurality of units of the generation device of thepresent invention are configured by units of a plurality of layershaving differing qualities. The dividing means may be configured todivide a set composed of the plurality of units into a plurality ofsubsets in which each subset is composed of units of the same layer.

In the above-described configuration, the generation device divides, forexample, base-layer data and enhancement-layer data coded byhierarchical coding into differing subsets.

Therefore, the reproduction device can select whether to receive onlyeither of the base-layer data and the enhancement-layer data that are ofdiffering layers in this way, or both.

In addition, the generation device of the generation device of thepresent invention is a generation device that generates a packetincluding one of a plurality of units generated by dividing each of aplurality of cbomponents composing a content. The first transportsequence assigning means may assign, to the packet including a unit,information indicating the transport sequence of the unit within theplurality of components as the first transport sequence information, foreach of the plurality of units. The packet generating means may generatea packet including the first transport sequence information, the secondtransport sequence information, and component information indicating thecomponent in which the unit is included.

In the above-described configuration, division is performed such that aplurality of units of a plurality of components are included in acertain subset. The divided unit generates a packet including thetransport sequence of the unit within a plurality of components, thetransport sequence of the unit within the subset, and componentinformation indicating the component of the unit, among the plurality ofcomponents.

Therefore, the reproduction device that has received the packet ismerely required to receive only the packets of the required component byreferencing the component information. The process for requestingretransmission of a packet to the generation device when the packet ofanother component is not received can be omitted.

INDUSTRIAL APPLICABILITY

The present invention can be used in a transmitter that transmitscontent over a network and a receiver that receives content over anetwork.

REFERENCE SIGNS LIST

-   1 transmitter (generation device)-   10 transmitter control unit-   11 transmitter storage unit-   12 transmitter communication unit-   13 content dividing unit (dividing means)-   14 header generating unit (packet generating means)-   15 transport sequence assigning unit (first transport sequence    assigning means and second transport sequence assigning means)-   16 content-   2 receiver (reproduction device)-   20 receiver control unit-   21 receiver storage unit-   23 display unit-   24 sound output unit-   25 header analyzing unit (detecting means)-   26 decoder-   27 reproduction control unit (reproducing means)-   3 content transmitting and receiving system

1. A reproduction device that reproduces media units, the reproductiondevice comprising: a receiving circuit receives a packet; a detectingcircuit that detects, from the packet, one payload of a plurality ofpayloads included in a package, a payload type indicating that a mediaunit is included in the payload, first transport sequence informationindicating a transport sequence of the payload within the package,second transport sequence information indicating a transport sequence ofthe payload within a subset of the package, and a flag indicatingwhether or not the first transport sequence information is included inthe packet; a decoding circuit that decodes the media unit in a casethat the payload type indicates that the media unit is included in thepayload; and a reproduction circuit that reproduces the media unit,wherein the detecting circuit detects the first transport sequenceinformation when the flag is equal to
 1. 2. A generation devicecomprising: a generating circuit that generate a packet, wherein thepacket includes one payload of a plurality of payloads included in apackage, a payload type indicating that a media unit is included in thepayload, first transport sequence information indicating a transportsequence of the payload within the package, second transport sequenceinformation indicating a transport sequence of the payload within asubset of the package, and a flag indicating whether or not the firsttransport sequence information is included in the packet; a settingcircuit that sets a value of the flag equal to 1 in a case that thefirst transport sequence information is included in the packet.